Carrera Injectors Questions: Help
 

So my car is misfiring like crazy. It's been getting worse and worse for the past year or so. I haven't had time to fix it.

Now, running the car in the cold, it's misfiring bad enough to make the car shake at anything below 2500rpm. Enough is enough! I am fairly certain I don't have bent valves, and I've eliminated most of the other causes of misfiring. My cap and rotor are a year old, secure, and the plugs and wires are brand new.

I have also test-torqued a couple of intake runner bolts. They are secure. I also know for a fact that my #6 cylinder is running colder than the others.

I have run techron through the car twice, no effect. The car is getting close to undriveable now. So I am going to start with the injector o-rings.

How do I go about replacing them on my Carrera? Any insight is appreciated.

i wish I knew what it was Mark.. I'd swing down and give ya a hand..
Sorry.. I have faith someone will have the answer!! or we're all DOOMED!!!... wha... yes DOOMED!!!!

Eric

The injectors come out easily enough. Just unplug the wires going to each of them (marking them with colored taped first, of course), maybe uncrew the rail holding the wires and give each injector a good yank. They just pop out. I can't remember exactly how my Carrera injectors looked, but the last time I saw one for a 3.0, I think the O-rings looked pretty easily peel off and replace.

Have you checked for vaccuum leaks? I had a few with bad intake manifold gaskets. Are you running too rich?

Well, the o-rings are easy enough to replace from what I've seen. I don't think I'm running too rich since the plugs I'm pulling out are pretty white - not at all fuel-soaked or even brownish. It's running lean when it's running, so I'm sure there's too much air getting in there, and my first place to go with that is the o-rings. After that, I will probably take it to a mech to redo the intake manifold gaskets.

.........or not enough fuel.

Mark,

Can't remember if you were the one who previously had problems with the reference sensors or the cyl. head temp sensor. Look at the reference sensors to see if the wiring is good- this is how they go bad. Sheathing splits and wires get contaminated.

Injectors seem unlikely if Techron doesn't make much difference? But, a problem that progressively gets worse like this could be due to injectors. To satisfy your injector theory, start by removing and reattaching each injector lead one at a time to see how that changes the characteristics of the motor. Pull one wire off, see what that does, reconnect it and move to the next and do the same.

O-rings are not likely to be the problem, but the injector(s) itself. Bad o-rings would be a noticeable smelly leakage problem. You gotta pull pretty hard to get the rail off the manifold, so be ready. Just make sure you have all the screws out........there's no maybe here. Don't gorilla with the rail too much or you can disturb that pesky main fuel line that goes under the manifold. You don't want that sucker to start leaking. $300..........

After all your fuel issues are satisfied, don't rule out the airflow meter. I kinda remember people saying this bugger can cause driveability problems when not operating right.

Check the basic stuff. Air, fuel, spark.

This just came to mind..................... Check for keywords like injector or whatever with Kurt B username. I remember him having a problem similar to this???? Worth a shot.

Man, I really don't want to go having to replace injectors. At $70 a pop, that gets expensive to even start.

The cyl head temp sensor and flywheel reference sensor were both replaced last winter. So those are pretty likely okay.

I *do* have an odd fuel-ish smell coming from the car, actually.

Simple first round of checks should also include intake manifold gasket bolts.....see if they're loose and torque them down a bit...not too much because you're compressing a soft rubber gasket. Another ( and likely) source of unmetered air to enter...

---Wil Ferch

A data point: I had a bad injector in my 3.2 once and the difference was very subtle when just 1 of the 6 was "bad". At least at idle.
-Chris

Yeah, those injectors aren't cheap. Check 'em one at a time and see what happens.

The fuel routing on a Carrera is pretty straightforward in the engine bay. The system starts from the filter, goes into the infamous bent Y-shaped fuel line, thru the rails to the injectors. Also in the system is the the regulator------>damper section at the front (front of the car) of the fuel rails, joined by another rubber crimp line. This section of the system sends the remaining fuel thru the return line to the fuel tank.

Good that the ref. and CHT parts are good. Those are kind of a pain to replace with the motor in the car.

How does the car run above 2500?

Souk got a load of bad gas at Gingerman and his car ran awful, not wanting to pull in the upper rpms. Turned out to be as simple as a fuel filter. Tried replacing coils, WUR's,........... turned out to be crud in the fuel that clogged up the filter.

No personal experience, but 944T injectors are supposedly a nice upgrade, if you do end up needing to replace them.

My '84 started running worse & worse - to the point that it hardly ran below 3k RPM. Above that, it seemed fine. Techron didn't help at all. I had the injectors refurbished by Marren Fuel Injection. http://www.injector.com/index.php

I think it cost about $150 and about a two-day turnaround. At the same time, I replaced my intake gaskets which had shrunk and hardened. Another issue was oxidation on two of the injector connections. Marren told me which ones because I had numbered the injectors - 5&6 had a green patina on the connections resulting in a high resistance. Once done, the car ran better than it ever had since I'd owned it.

YMMV

I would take a good look at the intake gaskets. Shoot some carb clean while at idle and listen for a increase or decrease in RPM. Mine were actually blown out even though the bolts were tight. Also listen for a whistle sound while shuttiing the engine off.

Mark,

If you can find an official Bosch service center, take out all six injectors and have them tested. If marginal, see if the Bosch shop can have the injectors cleaned overnight in a heated ultrasonic cleaner ... in a vat full of Berryman's B-12 Chemtool, at 140°F.

If not able to find a shop capable of cleaning as specified above, consider sending them off to be reconditioned and flow matched at Marren's. Here is an old thread with more details:

http://forums.pelicanparts.com/showthread.php?s=&threadid=9094&highlight=flow+mat ched+injectors

mark

i have had a similar problem for some time. it comes and goes especially when its wet out.

injectors dont have an indefinite service life so its money well spent servicing or replacing them.

i wonder whether my problem is electrical though.

Classic Beru ignition cable symptoms telling you they need to be replaced.


Cheers,

Joe

What drove you to believe it is injector related?
How do the plugs look?
If one plug is fouled, replace it and move that cylinders injector to another location, and see if the problem follows...

Agreed, test resistance values of ignition cables, especially paying attention (inspecting) the connections at the plug.

You should also be checking your fuel pressure, that would be #1 before replacing any injectors. Find a qauge and hook it to the test port on drivers side injector rail most near the rear of the car (remove heat blower to tube to find test port on rail).

A ca-bashed injector would cause power loss, rough running, etc. but not necessarily an idle/idle/idle/spat/idle/idle/spat condition...

Best of luck-
BG

edit: just reread you had new wires. You might check them again anyway...

i replaced mine with magnorcore wires a year or so ago....

i wonder whether the dampness is in the distributor cap - i'm so lazy i havent checked it out yet.